[#419] rpc/client: Block until client connection is up

In previous implementation `Client` didn't block until the connection is
up on dial stage. This caused the dial timeout to have no effect.

Provide `WithBlock` dial option to `DialContext` call in `openGRPCConn`
method. From now `Client` blocks for configured timeout until the
connection is up.

Signed-off-by: Leonard Lyubich <ctulhurider@gmail.com>

rpc/client/connect.go

@@ -49,10 +49,16 @@ func (c *Client) openGRPCConn() error {
 
 	dialCtx, cancel := context.WithTimeout(context.Background(), c.dialTimeout)
 	var err error
-	c.conn, err = grpcstd.DialContext(dialCtx, c.addr, grpcstd.WithTransportCredentials(creds))
+	c.conn, err = grpcstd.DialContext(dialCtx, c.addr,
+		grpcstd.WithTransportCredentials(creds),
+		grpcstd.WithBlock(),
+	)
 	cancel()
+	if err != nil {
+		return fmt.Errorf("open gRPC client connection: %w", err)
+	}
 
-	return err
+	return nil
 }
 
 // ParseURI parses s as address and returns a host and a flag